The present invention is directed generally to centrifugal fluid separation devices and is more particularly concerned with a pressure driven and/or balanced separation device preferably having a disposable, non-invasively driven, loopless rotor disposed in a rotating-sealless relationship with the entry and exit flow tubing lines.
A number of fluid separation devices have been known and various models are currently available for the separation of blood or other composite fluids into the various component elements thereof. For example, a variety of centrifugal machines are available for separating blood into component elements such as red blood cells, platelets and plasma, inter alia.
Centrifugation for such purposes has come in many forms in both continuous and batch types. For example, in the widely used process known as continuous centrifugation, as generally opposed to batch process centrifugation, a continuous input of a composite fluid is flowed into the separation device or chamber while at the same time the components of that composite fluid are substantially continuously separated and these separated components are usually then also substantially continuously removed therefrom. Many currently popular forms of such continuous fluid separation devices include loops of entry and exit flow tubing lines connected to the separation centrifuge chamber such that each loop is rotated in a relative one-omegaxe2x80x94two-omega (1xcfx89-2xcfx89) relationship to the centrifuge chamber itself so that the tubing lines will remain free from twisting about themselves.
An alternative form of tubing line connection to a continuous centrifugal separation device is also available in the art which does not have such a loop, but which instead requires one or more rotating seals at the respective connections of the tubing line or lines to the centrifuge separation chamber, again to maintain the tubing lines free from twisting.
Batch-type centrifugation, on the other hand, usually involves separation of a composite fluid such as whole blood in a closed container, often a deformable bag, followed by a usually complicated process of automated and/or manual expression of one or more of the separated components out of the separation container or bag. A great deal of control, either automated, such as by optical interface detection, or by a diligent human operator watching a moving interface, is required with such previous batch-type processes. Indeed, various means and methods have been used in prior centrifugal separation devices both continuous and batch, for driving fluid flow and for maintaining desirable interface position control between the component elements being separated thereby. For example, as mentioned, many optical control feedback methods and devices have been employed in the art. Various pumping and valving arrangements are also used in various of these and other systems. Alternative, relatively automatic volume flow and density relationship interface controls have also been used. For example, in a continuous system, control outlet ports may be disposed in strategic locations relative to the separated component outlet ports.
Nevertheless, many facets of these prior separation devices, though satisfactorily productive, may provide certain features which are less efficient than a desired optimum. For example, centrifugal separation devices using loops of tubing lines rotated in the above-described 1xcfx89-2xcfx89 relationship with the centrifuge separation chamber generally require significant, usually large drive mechanisms which thereby mandate that each such entire device then also be necessarily of a relatively large scale. Rotating seal devices, on the other hand, require intricate and often operationally problematic rotating seal structures. Sterility may also be an obstacle for rotating seals. Still further, many prior drive and/or interface control systems have either been overly complex as in the case of most of the optical control models, and/or automatic volume flow/density controls may not be as desirably efficient in separation due to the usually inherent re-mixing of some quantities of the centrifugally separated components.
Hence, substantial desiderata remain to provide more highly efficient centrifugal separation devices in terms of increased efficiency fluid flow drive and separation interface controls; reduced rotor drive mechanization, quantity and/or scale; and/or reduced seal need and/or intricacy. It is toward any one or more of these or other goals as may be apparent throughout this specification that the present invention is directed.
The present invention is directed generally to centrifugal separation devices and/or systems for use in centrifugally separating composite fluids into the component elements thereof. Such centrifugal separation devices and/or systems include unique centrifugal rotor and rotor housing combinations in which each rotor may be disposed in a freely rotatable disposition relative to the rotational device housing. Freely rotatable indicates loopless and rotating sealless as well as a preference that these rotors may be magnetically or otherwise non-invasively driven. A totally closed system may thus be provided with simple sterilization and disposability of the rotor and/or the rotor/housing combination and/or the tubing set associated therewith.
Each rotor has a substantially central fluid receiving/containing area and several fluid flow channels defined therein. In a preferred embodiment, a composite fluid to be separated into component parts may then be delivered to the fluid receiving area from which it may travel under centrifuge conditions through a fluid transport channel to a circumferential fluid separation channel where it may be subjected to substantial centrifugal forces which may separate the composite fluid into respective components. These components may then travel to distinct first and second separated fluid outlet channels. The separated fluid components may then exit from these outlet channels and may then be moved from the separation device to a collection bag for storage or further processing or may then be returned to the donor. The composite fluid may be of various sorts, but is preferably whole blood, and the respective components may then be plasma and red blood cells (RBCs), although buffy coats and/or platelets, inter alia, may also be separated and harvested herewith.
The inlet channel and the first and second fluid outlet channels are preferably pre-selected to have respective inlet and first and second outlet lengths or xe2x80x9cheightsxe2x80x9d (or relative radial distances) that are selected to be related to each other so as to provide a substantial hydraulic or hydrostatic fluid pressure balance between the outlets for the respective separated fluids flowing therethrough. Such a pressure relationship provides for forcing the fluid flow and the outlet balance preferably controls the desired location of the interface between the separated fluid components within the circumferential separation channel. The preferred outlet channel length or height relationship which provides this hydraulic balance may be derived from the general hydrostatic equation xcfx812g2h2=xcfx813g3h3 wherein the length or height of the first outlet channel in this equation is h2, and the length or height of the second outlet channel is h3. These relative lengths or heights, h2 and h3, may then be selected so as to provide the appropriate preferred pressure balance given a separating composite fluid to be flowed in separated fluid component parts therethrough. The other variables in the above equation are either fluid dependent, see e.g., xcfx812 and xcfx813 which represent the respective densities of the separated fluids in the first and second outlet channels, or are otherwise relatively non-selectable and/or for the most part not as consequential or are relatively non-governing in the general equation, e.g., the g2 and g3 variables are gravitational or centrifugal acceleration values preferably representing the respective average g value in each of the two columns, which may be a similar, if not a substantially equal value (i.e., even though there is likely a distinction, g2 may generally vary a relatively small amount from g3) in normal operation. Hence, the dominant, selectable driving differences will be in the relative heights h2 and h3 which may simply be chosen to accommodate for any differences in the other terms, xcfx81 or g.
Thus, for a composite fluid such as whole blood, where the respective densities of the separable component parts, e.g., plasma and RBCs, are known (within sufficiently controllable ranges), then the respective heights, h2 and h3 may be chosen to appropriately set the location of the interface of separated components therebetween. This interface will thus remain where desired, preferably in the separation channel notwithstanding a substantially continuous inflow of composite fluid to be separated and a substantially continuous outflow of separated components.
Other similarly derived relationships of interest particularly relative to the dynamic forcing of the fluid flow in this invention, inter alia, are also involved in the systems of the present invention. For example, a further preferred aspect of the present invention involves a preferred relationship between either of the outlet fluid pressure term(s) and the inlet pressure term, particularly as these are impacted by the selection of the outlet channel heights or lengths h2 and h3 as described above, as well as the selection of the inlet channel height or length h1. Here, the fluid will flow in a continuous forward fashion so long as the inlet fluid pressure term xcfx811g1h1 is at least greater than either of the outlet fluid pressure terms xcfx812g2h2 or xcfx813g3h3. In an equation form, this relationship is;
xcfx811g1h1 greater than xcfx812g2h2 or xcfx813g3h3.
This relationship governs a general forcing of the fluid flow in one direction out of the initial receiving/containment area, into the separation channel and from there, into the respective component collection areas. In the preferred embodiment where xcfx812g2h2=xcfx813g3h3, then the inlet pressure term xcfx811g1h1 will be greater than both of the outlet pressure terms simultaneously.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended merely to provide limited explanation of the preferred embodiments of the invention as more broadly claimed. These and further aspects of the present invention will become clearer from the detailed description read in concert with the drawings in which like component elements are referenced therein with like component numbers throughout the several views.